1. Field
One or more embodiments relate to a piezoelectric acoustic transducer and a method of fabricating the piezoelectric acoustic transducer.
2. Description of the Related Art
Piezoelectric acoustic transducers convert between acoustic energy and electrical energy by using a piezoelectric phenomenon. Examples of piezoelectric acoustic transducers include micro-speakers that convert electrical energy into acoustic energy and microphones that convert acoustic energy into electrical energy.
For example, piezoelectric acoustic transducers include a vibration plate in which a first electrode, a piezoelectric layer, and a second electrode are stacked on a diaphragm, where the piezoelectric acoustic transducers expand or contract the piezoelectric layer by applying voltages to the first and second electrodes to vibrate the vibration plate. These piezoelectric acoustic transducers may vibrate the vibration plate without using an additional magnet or driving coil. Thus, the structure of the piezoelectric acoustic transducers is simpler as compared to voice coil type acoustic transducers such as electro-dynamic speakers.
As miniaturized electronic devices such as mobile phones or personal digital assistants (PDA) have been developed, the technology for miniaturizing acoustic transducers for use in the miniaturized electronic devices has also been developed. In this regard, piezoelectric acoustic transducers having a simple structure are easy to be miniaturized. In the technology for miniaturizing piezoelectric acoustic transducers on a silicon wafer by using micro-electro-mechanical systems (MEMS), piezoelectric acoustic transducers may be fabricated with a semiconductor fabrication process, and thus, fabrication costs may be reduced. Also, a plurality of circuits may be included in a single chip, and thus, an acoustic device may be miniaturized.
The piezoelectric acoustic transducers may be fabricated in a comparatively simple process and may be easy to be miniaturized. However, in these piezoelectric acoustic transducers, acoustic output or sensitivity is lower than in voice coil type acoustic transducers.